SUBSTRATE AND XENOBIOTIC UTILIZATION PATTERN AND HALOTOLERANCE OF AZOSPIRILLUM BRASILENSE AND A. LIPOFERUM NATIVE ISOLATESR. Gowrisankar, C. Mariappan, R. Palaniappan and C. Meenakshi Sundaram
The sediment and water samples from a cultivated paddy field were screened for the presence of Azospirlium sp. and the isolates were identified up to species level. Among the Azospirllum native isolates, A. brosilense SPKO I and A. Iipoferum SPK02, isolates were inclued in this study. The ability of these two bacterial species in utilizing a variety of sugars and organic acids as carbon source and their salt tolerance were evaluated. Further, their xenobiotic resistance and utilization pattern was tested with different concentrations of dimethoate (pesticide) and butachlor (herbicide). Both the Azospirillum isloates were able to utilize glucose, lactose and maleic acid efficiently, starch, mannitol and tannic acid moderately and were unable to utilize acetic acid as a carbon source. The native Azospirillum isolates namely, A. brasilense SPK 0 I and A lipoferum SPK 02 were exceptionally sensitive to tested farm chemicals even at low concentrations. Moderate growth of these test isolates was observed with dimethoate as a sole carbon source that too at a very low concentration (0.01%, Al). This study strongly suggests the necessity of employing xenobiotic resistant Azospitillum isolate as biofertilizer in crop fields, which invariably/inevitably are exposed to a variety of farm chemicals such as dimethoate and butachlor.
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